Methyldopa (L-Alpha-methyl-3,4-dihydroxyphenylalanine) is used for the treatment of hypertension, and is listed as one of the top 25 drugs in the United States, with over 22 million prescriptions written per year. Side effects of methyldopa have included sexual dysfunction in humans, and in the NTP subchronic studies testes and uterus were reported to be target tissues in the Fischer 344/N rats. This NTP intramural research project is designed to determine the potential toxic effects of methyldopa on the reproductive system of male Fischer 344/N rats. Methyldopa was administered for eight weeks at doses of 0, 50, 100, 200 and 400 mg/kg. Treated male rats were mated to untreated female rats. Male rats were evaluated for histopathologic abnormalities in the reproductive organs and sperm abnormalities. The results of the mating trial, histopathologic analysis, and sperm analysis are currently being evaluated.